Stabilization of photographic glyoxal hardening solutions with water soluble boron compounds



Patented Mar. 2,

STABILIZATION OXAL HARDENING WATER SOLUBLE BO James E. Bates,

OF PHOTOGRAPHIO GLY- S OLUTION S WITH RON COMPOUNDS Chenango Bridge, and John G.

Hainsworth, Endicott, N. Y., assignors to General Aniline & Film Corporation, New York,

N. Y., a corporation of Delaware No Drawing. Application December 6, 1950,

Serial No.

6 Claims.

This invention relates hardening solutions ingthe same. r In the processing of gelatino silver halide emulsions, particularly in color film, it is the practice to treat the emulsions with a hardening compound so as to reduce the tendency of the gelatin to soften or distend during processing of the photographic material containing the gelatino silver halide emulsions, particularly at temperatures higher than those specified for processing the particular photographic material. Compounds which have been used for hardening gelatin in silver halide emulsions are alum, potassium chrome alum, and aliphatic aldehydes, such as formaldehyde, hydroxyaldehydes, acrolein, and the like. Of these, formaldehyde has :been extensively employed in view of its cheapness and commercial availability.

to stabilized glyoxal and to a method of preparagent, it possesses the undesirable property of producing fog, desensitization or change of contrast when used prior to the development step.

Within recent .years, glyoxal has attained prominence as a hardening agent for photographic gelatino silver halide emulsions. Aqueous alkaline solutions of glyoxal are suitable for the hardening of color film prior to rapid processing at elevated temperatures. It treatment with such a solution is omitted, excessive swelling and reticulation of the emulsion layer or layers occurs. Alkaline glyoxal hardening solutions, however, are unstable. The pH falls on standing, possibly due'to the oxidation of the glyoxal to glyoxylic and/or oxalic acid, and the solution becomes ineffective as a hardener. The useful life of an alkaline glyoxal solution containing an alkali metal carbonate as the alkali is approximately 6 hours, and as the solution ages, the reduced hardening causes not only reticulation but also a change in film speed and color balance.

Accordingly, it is an object of the present invention to provide stabilized alkaline glyoxal hardening solutions.

A further object is to stabilize such alkaline solutions by the addition of water soluble boron compounds in stabilizing amounts.

Other objects and advantages will appear hereinafter from the following description.

We have found that the foregoing objects are readily accomplished by th addition of a stabilizing amount of a water soluble boron compound to alkaline glyoxal hardener solutions. Alkaline glyoxal hardener solutions generally Although formaldehyde is satisfactory as a hardening' consist of 0.04 to 2% Of glyoxal of low formaldehyde content and 0.1 to 3.0% of an alkali metal carbonate, such as sodium, potassium, or lithium carbonate, or equivalent amounts of their hydrates, per liter of water with or without the presence of other adjuvants. Such solutions may contain, if desired, 0.03 to 0.06% of a water softener compound, such as, for example, sodium hexametaphosphate, ethylenediamine-tetraacetic acid and its alkali salts, sodium gluconate, the sodium salt of glucoheptonic acid, and the like, 1.0 to 6.0% of an alkali metal sulfatasuch as sodium or potassium sulfate, and 0.001 to 0.1% of an azole, such as Z-mercapto-benzimidazole, phenylmercaptotetrazole, 2 mercaptobenzothiazole, benzotriazole, 6-nitrobenzimidazol and the like. A small quantity of formaldehyde may be added for stain reducing purposes, if desired.

The purpose of the water softener compound is to prevent sludging in case soft or distilled water is not available. The alkali metal carbonate or any other strong alkali is added for the purpose of establishing a pH which accelerates the hardening action of the glyoxal on the gelatin. Optimum results are obtained within a DH range extending from 9 to 11. The alkali metal sulfate is believed to reduce swelling of the gela-v tin so that the hardener may work more efllciently. The azole reduces the fogging tendency of the glyoxal alone or in the presence of small amounts of formaldehyde.

Some of the water soluble boron compounds which have been found to be suitable as stabilizing agents for the alkaline glyoxal prehardening solutions, include boron acids and their water soluble salts, e. g., borax, sodium metaborate, sodium perborate, orthoboric acid, and polyboric acids, such as those characterized by the formulae H6B409, H4B6011 and H2B10O1s as well as organic derivatives of boric acid, such as benzylboric acid, C7H1B(OH)2 or ethyl boric acid, C2H4B(OH)2,'and thelike.

The stabilizing proportions of boron compounds to be added to the solution may vary from 0.5 gram to 20 grams per liter of alkaline glyoxal solution. Th addition of these proportions or higher, since they are not critical, causes no adverse effect upon the film speed and stabilizes or preserves the solution for at least 24 hours. With tap water as the solvent for the solution, the keeping quality is enhanced by 18 to 20 additional hours. The boron compounds not only stabilize the hardening action, but also reduce to a minimum the detrimental eiiects of the use of an aged and unstabilized hardener on photographic speed and color balance. In order to better disclose the invention, the following examples are, furnished, it being understood that these examples are illustrative. only and are not intended to limit the scope of the: invention.

Example I A glyoxal solution was preparedaccording to The above hardening solution when used for 2 minutes at 80 F. prior to development and subsequent processing, hardens a multilayer color'film, sufficiently to permit rapid processing at the same high temperature instead of the normally recommended temperature of 68 F. without aflecting the speed and color balance of the film.

The color film used had three light sensitive layers which were sensitized to the blue, green, and red' regions of thespectrum respectively. Each layer contained color formers fast to diffusion; and capable of yielding upon color development with an aromatic primary amino developing agent, dye images complementary in color to the color for which-the layer was sensitized.

The exposed and hardened color film was developed for 6-minutes in a black and white (first) developer, shortstopped for 1 minute, washed for Z'minutes, given a second (reversal) exposure, color developed for 4 minutes in a suitable color developer, shortstopped for 30 seconds, bleached. for 1%v minutes, fixed for 2 minutes,.and washed for 1 /2 minutes...

The. total processing time. was cut from the conventional .SSminutes to less than 20v minutes. The; advantage. of. hardening the. exposed film prior; to: development is that customary intermediate hardening. treatments can be omitted. The processing. time is. also. reversed by virtue of higher processing temperatures.

Example If Example I. was repeated. with the exception that 2.0 grams of sodium metaborate wereused inplace of 2.0 grams of sodium perborate.

Example HI Example I-V Example I was repeated with the exception 4 that 1.0 gram of boric acid was used in place of 2.0 grams of sodium perborate.

In all four instances, the addition of the water soluble boron compounds. extended. the useful liieof the hardener solution. tov at least 24 hours, whereas a hardener solution containing no such compounds became utterly useless after 6 hours.

While we have disclosed the preferred methods of. our. inventiornit. will be readily apparent to those skilled in the art that many changes and variations may be made in the proportions of the hardening solution without departing from the. spirit. thereof- The scope of the invention is,,therefore,pto be limited solely by the appended claims.

We claim:

alkaline glyoxal hardening solution for photographic film, comprising 0.04 to 2.0% of glyoxal, an amount of alkali sufiicient to establish a pH range extending from 9 to 11, and a stabilizing amount of a compound selected irom the class consisting of. boronacidspand. the-war ter soluble salts thereof.

2.. .An alkaline glyoxal hardening solution comprising 0.1.to 3.0% of alkalimetal carbonate,- 0.04 i to 2.0 %v of glyoxal, and a stabilizing amountof sodium perborate.

3. An alkaline.- glyoxal prehardening; solution comprising 0.1 to 3.0%v of alkali metal carbonate, 0.04 to 2.0% of glyoxal; and a stabilizing amountof borax.

4. An alkaline glyoxal .prehardening, solution comprising 0.1 to*3.0 or alkali metal carbon.- ate, 0.04 to 2%.. of glyoxal. anda stabilizing amount of boric acid.

5. An alkaline. glyoxal prehardening: solution comprising. 0.3. to. 3.0% of. alkali; metal. carbureate,,0.04 to 2.0% of glyoxaLxand a.stalciilixing. amount of sodium .metaboratm 6.. An alkaline glyoxal hardening solution-dim. photographic filmcomprising '0.1.to'.3:% of alkali metal: carbonate,v 0.04. to. 20% of glyoxal, .and: a stabilizing amount of: a compound. selected from thecl'ass consisting of-boronracidsxand the. water soluble salts thereof.

JAMES E. BATES.

JOHN G.- MAINS,VVOlt'zl'Jfli.v

References Cited in thefilerof patent.

Beachell June 27,1950 

1. AN ALKALINE GLYOXAL HARDENING SOLUTION FOR PHOTOGRAPHIC FILM, COMPRISING 0.04 T 2.0% OF GLYOXAL, AN AMOUNT OF ALKALI SUFFICIENT TO ESTABLISH A PH RANGE EXTENDING FROM 9 TO 11, AND A STABILIZING AMOUNT OF A COMPOUND SELECTED FROM THE CLASS CONSISTING OF BORON ACIDS AND THE WATER SOLUBLE SALTS THEREOF. 